1. Field of the Invention
The present invention relates to a mold fixture for use with alignment, installation, extraction, and storage of a mold tooling.
2. Description of the Background Art
Resin Transfer Molding (RTM) is a commonly used fabrication process for the manufacture of fiber-reinforced composites. The resulting light-weight, high strength parts are desirable for a variety of applications. Examples of such applications are commercial items such as chairs, automobile parts and aircraft components.
RTM is typically limited to low viscosity resin systems. The RTM process is fairly simple. A two-part, matched-metal mold (or tool) is made, which has a mold cavity conforming to the shape of the desired part. A preform is placed into the mold cavity, and the mold is closed. The resin is then injected under pressure through injection ports into the mold and follows pre-designed paths, impregnating the preform. After the fill cycle, the cure cycle begins, during which the mold can be heated and resin polymerizes to become rigid plastic. Both the mold and resin can be heated as needed for the application.
RTM tooling requires a method to align the mold halves, a way to introduce resin in the mold, vents to let the air out, a seal to keep the resin in the tool and a method of clamping the tool set together. In addition, the forces acting on an RTM tool demand a well-designed structure including a substantial supporting framework. It is important to establish a highly accurate mold set alignment during the mold building sequence. An effective method of alignment is to use core box pins. These pins are molded in the male and female halves of the tool set and provide an unchanging positive alignment.
RTM can utilize either “hard” or “soft” tooling, depending upon the expected duration of the run. Soft tooling would be either polyester or epoxy molds, while hard tooling may consist of cast machined aluminum, electroformed nickel shell, or machined steel molds. RTM can take advantage of the broadest range of tooling of any composites process. Tooling can range from very low cost to very high cost, long life molds.
Well known in the art is the use of a mold base (or frame), which receives a mold insert (or die insert). Respective halves of the mold insert form an internal injection cavity when clamped together. In order to re-tool a molding apparatus, for example when the desired product is changed, the mold inserts are removed from the mold base and replaced with a different set of mold inserts. An example of such mold frames and mold inserts are those made by the Master Unit Die Products of Greenville, Mich. identified as “MUD” (Master Unit Die) frames and unit die inserts. These frames and inserts are designed to be used in matching pairs wherein the large frames are each arranged to accommodate in a recess of the frame a corresponding die insert.
In order to maintain dimensional stability, the frames are of a heavy construction, generally steel, and, in order to change from one size die insert to another die insert, the first die insert is removed from the frame and replaced with a second die insert.
Because this operation involves a substantial rearrangement of the molding machine and involves the handling of a heavy frame, the operator time and down time for the molding apparatus are a substantial part of the molding process. In particular, because such a changeover may occur daily or even more than once a day, the changeover time is a significant part of the cost of producing the molded product.
Furthermore, in view of the heavy weight of the mold, it is difficult to place the mold into the molding machine and to remove the mold from the machine when the machine is to be used to form a different part. If the mold is not raised and lowered carefully, and because of the heavy weight of the mold or mass imbalance, it becomes very difficult to replace the mold without damaging the mold or the injection molding machine. Additionally, once the mold is removed from the molding machine, the mold must be stored, which is conventionally done by placing the mold onto a pallet and transporting the mold to a storage location.
U.S. Pat. No. 5,992,208 discloses a press arrangement that has sliding tables. These sliding tables carry molds between press stations and are provided in the press stations. An intermediate station is arranged between press stations, this intermediate station containing workpiece holders for the workpiece transport. There, however, arises the problem that the heavy mold must be slid across the sliders by the operator, which can result in injury. Furthermore, there is no provision for efficiently removing the mold from the press arrangement safely and securely, nor are there any provisions for storing the mold once it has been removed.
Because tooling cost and start up time comprise a substantial portion of the cost associated with RTM, a need has arisen for safer and faster initial setups, production changeovers, and storage.